1. Field of the Invention
The present invention relates to a bearing device having a rolling bearing fitted on a shaft. This bearing device can be utilized, for example, in the fields of a vehicular hub unit or a guide roller of the slide door of an automobile, and in other general fields of bearing devices.
2. Description of the Related Art
With reference to FIG. 17, a vehicular hub unit will be described as one example of the bearing device. In this hub unit B, a double row angular contact ball bearing 82 with vertex of contact angles outside of bearing is fitted on a journal 81 of a hub wheel 80. The free end of the journal 81 is rolled-caulked to bend radially outward. This bent caulked portion 85 is pushed onto the outer end face of an inner ring 84 of the bearing 82. As a result, the bearing 82 is so fixed on the hub wheel 80 as to be prevented from coming out.
The caulked portion 85 is so curved as to have an entirely roundish outer end face, as shown in FIG. 18. The curve at the outer end face of the caulked portion 85 has a single radius of curvature r0.
The cylindrical free end of the journal 81 at the hub wheel 80 is rolled-caulked by using a caulking jig 90, as shown in FIG. 19. At this time, the leading end of the caulking jig 90 is applied to the journal 81 and is rolled at a predetermined angle xcex8 on a single-dotted line O. As a result, the free end of the journal 81 is bent radially outward so that the inner ring 84 is prevented from coming out by the bent caulked portion 85.
In the example of the prior art thus far described, the shape of the outer end face of the caulked portion 85 is not strictly managed. This outer end face of the caulked portion 85 usually has a roundish shape. As a result, the shape of the caulked portion 85 may disperse for the caulking works. In an extreme case, the radially intermediate portion of the caulked portion 85 may leave and float over the inner ring 84. In this case, a resistance to a coming-out load, i.e., a coming-out resistance has a tendency to fall short.
On the other hand, the outer end face of the caulked portion 85 may be formed of a curve having a single radius of curvature r0. The caulked portion 85 of this outer end face shape is achieved by a caulking treatment under a substantially constant pressure from the initial to final stages of the caulking process. In this case, too, there occurs the aforementioned defect.
Against this defect, it is conceivable to inspect the finished state of the caulked portion 85 visually after the caulking treatment. Since the outer end face of the caulked portion 85 has the roundish shape, however, it is impossible to confirm from the appearance whether or not the floating state has occurred.
It is, therefore, a main object of the invention to provide a bearing device which improves the coming-out resistance by the caulked portion.
Another object of the invention is to provide a bearing device which not only improves the coming-out resistance by the caulked portion but also facilitates a decision even when the caulked portion is to be visually inspected.
The features and advantages of the invention will become apparent from the description to be made in the following.
According to a first aspect of the invention, there is provided a bearing device comprising: a shaft having one axial end formed into a cylindrical shape; and a rolling bearing fitted on the one axial end of the shaft, wherein the rolling bearing is so fixed on the shaft as to be prevented from coming out by rolling-caulking the one axial end of the shaft to bend it radially outward and by pushing the bent caulked portion onto the outer end face of the inner ring of the rolling bearing, and wherein the region at the outer end face of the caulked portion from the bending start point to the outer circumferential edge is formed of a composite curve joining curved surfaces of at least two different radii of curvature.
In the bearing device of this first aspect, the radii of curvature of the individual curved surfaces of the composite curve are preferably set to the larger value at the radially outer side.
The caulked portion of this shape is specialized, for example, by adjusting the pressure on the inner ring in the caulking process. Depending upon the caulking mode, the caulked portion can be pushed at its substantially entire area substantially homogeneously onto the outer end face of the inner ring, and the axial thickness can be enlarged as much as possible. As a result, the coming-out resistance by the caulked portion can be increased more than the prior art.
According to a second aspect of the invention, there is provided a bearing device comprising: a shaft having one axial end formed into a cylindrical shape; and a rolling bearing fitted on the one axial end of the shaft, wherein the rolling bearing is so fixed on the shaft as to be prevented from coming out by rolling-caulking the one axial end of the shaft to bend it radially outward and by pushing the bent caulked portion onto the outer end face of the inner ring of the rolling bearing, and wherein a flat face extending in a radial direction is formed at a predetermined region of the outer end face of the caulked portion.
In the bearing device of this second aspect, the flat face of the caulked portion is preferably formed at the axially outermost end of the outer end face of the caulked portion.
The caulked portion thus shaped is pushed in its entirety to the inner ring in the process for forming the flat face so that the it can be easily fitted on the outer end face of the inner ring thereby to increase the coming-out resistance by the caulked portion more than the prior art.
Moreover, the flat face to be formed on the outer end face of the caulked portion can be said to provide a shaping feature. This will be reasoned in the following. If the caulked portion were entirely fitted on the inner ring, the flat face would be neatly formed. If even a portion of the caulked portion were floating over the inner ring, the flat face would have undulations. If the state of the flat face is employed as a reference for the decision when the finished state of the caulked portion is to be visually inspected, therefore, the visual decision is facilitated.
If the flat face is positioned at the axially outermost end of the caulked portion, on the other hand, it provides a reference plane for determining the axial width size of the caulked portion. By managing that flat face, therefore, the entire length size of the bearing device is easily set. On the other hand, the flat face provides a mounting reference plane for an object to be mounted on the bearing device of the invention, so that the axial size in the mounted state can be managed highly accurately.